The present invention relates to an apparatus for recording data on a recording medium such as a disc or a tape.
Recording mediums such as optical discs, magneto-optical discs or magnetic tapes on which audio signals are recorded as digital signals are widely used as recording mediums in which, for example, a piece of music, a sound or the like may be recorded or reproduced. A recording and/or reproducing apparatus has been developed for the above medium.
In particular, recently, a medium has become available (i.e., so-called mini disc) not only for reproducing a signal but also recording a piece of music or the like by a user which is known as a magneto-optical disc. In the case of a mini disc system, an audio signal reproduced from the disc is once stored in a buffer, and the stored signal is read out for playback output. It is a so-called shock proof function. Of course, such a technique may also be applied to a production only system such as a compact disc system.
In such a digital recording/playback system, a table of contents (TOC) is recorded as supervisory information on the recording medium for controlling a recording operation and/or a playback operation of the data. The TOC information is read out from the recording medium, such as a disc, in advance and is held on the side of the recording/playback apparatus so that upon the operation, the TOC information may be referenced and the various controls of the access position and the music may be executed.
As described in, for example co-pending application Ser. No. 08/196,469, filed by the same applicant, TOC information is provided in the case of a minidisc where a premastered TOC (P-TOC) is recorded in the form of pits as non-overwritable information and a user TOC (U-TOC) is magneto-optically recorded so as to be rewritable in response to the recording/erasing operation for the music or the like. With respect to the U-TOC, as described in co-pending application Ser. No. 08/050,536, filed by the same applicant, the data are modified in the memory in response to the recording/erasing operation, and the U-TOC area is rewritten on the disc at a predetermined timing in accordance with the modified data.
By the way, in general, a semiconductor memory integrated circuit (IC) is used as a data buffer or a recording means for holding the TOC information. Thus, the storage section used as the data buffer for realizing the so-called shock proof function requires a large capacity (about 1 to 4 Mbits). Accordingly, a dynamic RAM (hereinafter referred to as D-RAM) is usually used, which has a high degree of integration in comparison with a static RAM (hereinafter referred to as S-RAM). As described in U.S. Pat. No. 5,410,526 issued to Mukawa, since a relatively small capacity (for example, about 256 Kbits) is sufficient for holding the TOC information, a part of the RAM for the data buffer is allotted for the TOC information.
As is well known, the structure for a backup means in case of a voltage drop of the main power source for the D-RAM is complicated in comparison with the structure for the S-RAM. Also, the consumption of power would be increased for the D-RAM. Therefore, it would be difficult to take a sufficient countermeasure against an accidental power suspension.
Now, in the case where the D-RAM is used only for the data buffer of the recording/playback apparatus, such a problem is not so serious. However, in the case where the D-RAM has a function of the TOC information, if the TOC information is erased by the accidental power stop, there are many problems. For instance, if the U-TOC information were to be erased mid-way through the compiling work during the recording operation, it would be impossible to record suitable supervisory information on the disc. In the case where the supervisory information would not be renewed on the disc, none of the data recorded by the recording operation that far would be recorded, resulting in serious problems.
It is therefore necessary to provide a backup means for the D-RAM so that, in case of an accidental voltage drop and power suspension, at least the U-TOC information that has been renewed is not volatile for a certain period of time. Further, the U-TOC information may be written on the disc to thereby suppress the losing of the recording data as much as possible. However, because the memory is the D-RAM, the backup structure is complicated and the cost is increased as described above. In particular, it is difficult to realize compact and inexpensive equipment.
Furthermore, during the recording operation in the D-RAM, the U-TOC data are not actually periodically renewed at a timing in response to the data recording. As described in U.S. Pat. No. 5,453,767 issued to Mukawa, the supervisory information is renewed in the D-RAM in accordance with the data that has been recorded so far, and after the suspension, the U-TOC data that has been renewed is read out from the D-RAM and written on the disc. Thus, in the case of an accidental suspension of the power supply during the recording operation, even if the data of the D-RAM were to be held, the U-TOC data written thereon would be kept under the non-renewal condition. Otherwise, in the case where a temporary suspension occurs in the mid-way, under the renewal condition, a partial renewal happens corresponding to the data that has been recorded up to the temporary suspension. Accordingly, it is meaningless to backup the D-RAM.